On Thu, 2012-10-11 at 09:19 +0200, Simon Klinkert wrote: > On 10.10.2012, at 18:22, Peter Zijlstra wrote: > > > On Wed, 2012-10-10 at 17:44 +0200, Simon Klinkert wrote: > >> I'm just wondering if the 'load' is really meaningful in this > >> scenario. The machine is the whole time fully responsive and looks > >> fine to me but maybe I didn't understand correctly what the load > >> should mean. Is there any sensible interpretation of the load? > > > > I'll leave meaningful aside, but uninterruptible (D state) is part > of > > how the load thing is defined, so your 500 result is correct. > > Yes, the calculation of the load is correct but I still don't know how > I should interpret the load… > > On 11.10.2012, at 06:02, Mike Galbraith wrote: > > > Makes perfect sense to me. Work _is_ stack this high. We don't and > > can't know whether the mountain is made of popcorn balls or > boulders. > > That's the point. Afaik the D state never represents 'work'. These > processes are waiting for something.
Yeah, the whole pile is waiting, but they're not idle. There are N tasks pointed at CPUs. > > Let's say we have 10,000 processes in the D state (and thus a load of > ~10,000) doing nothing. What should the load tell me? The machine is > under fire? There is nothing to do? There might be something to do but > the machine doesn't know? They are doing something, just not at the particular instant you see them in D state. D state pushing load through the roof tells you that you have a bottleneck. Whether the bottleneck is a bit of spinning rust or insufficient NR_CPUS doesn't matter much, both are bottlenecks. -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
